Railroads have lubricated curved rail with trackside (wayside) lubricators to reduce friction between the flanges of the railroad car wheels and the rail. A pump in the wayside applicator is mechanically activated as a train passes and a stream of grease is applied to the gage face (a face engaging the wheel flange that is not the top running surface) of the rail.
Recently, railroads have discovered that the application of grease on straight rail (tangent track), can provide substantial benefits, such as up to 30% fuel savings, reduced wheel and rail replacements, and reduced derailments. Wayside applicators are now being supplemented by locomotive mounted applicators, hyrail applicators, and portable units mounted on trucks which run along the track and apply grease to the gage face of the rails. This has caused a substantial increase in the demand for rail lubricants.
Rail lubricants typically comprise molybdenum sulfide-, graphite-, and lead-containing soap-based or solids-containing greases. These rail lubricants are deficient for large scale use since lead and molybdenum sulfide are undesirable from an environmental and/or toxicological viewpoint, and graphite is opaque and messy, which makes maintenance of the applicators difficult, and is not very effective by itself in reducing friction.
The applicants have discovered that a non-Newtonian metal overbased colloidal disperse system is capable of achieving the desired economical reduction in friction between railroad wheel and rail, along with extreme pressure/anti-wear protection, without posing the environmental, toxicological and cleanliness problems of the prior art rail lubricants.
The terms "overbased", "superbased", and "hyperbased", are terms of art which are generic to well known classes of metal-containing materials which for the last several decades have been employed as detergents and/or dispersants in lubricating oil compositions. These over-based materials, which have also been referred to as "complexes", "metal complexes", "high-metal containing salts", and the like, are characterized by a metal content in excess of that which would be present according to the stoichiometry of the metal and the particular organic compound reacted with the metal, e.g., a carboxylic or sulfonic acid.
Newtonian overbased materials and non-Newtonian colloidal disperse systems comprising solid metal-containing colloidal particles predispersed in a disperse medium of at least one inert organic liquid and a third component selected from the class consisting of organic compounds which are substantially insoluble in said disperse medium are known. See, for example, U.S. Pat. Nos. 3,492,231; 4,230,586; and 4,468,339.
Carboxylic acid derivatives made from high molecular weight carboxylic acid acylating agents and amino compounds and their use in oil-based lubricants are well known. See, for example, U.S. Pat. Nos. 3,216,936; 3,219,666; 3,502,677; and 3,708,522.
Certain alkyl succinic acid/alkanol amine condensates have also been described; see, for example, U.S. Pat. No. 3,269,946. Water-in-oil emulsions containing alkyl and alkenyl succinic acid derivatives are also known; see, for example, U.S. Pat. Nos. 3,255,108; 3,252,908 and 4,185,485.
Surfactants are also well known. See, for example, the text entitled "Non-ionic Surfactants" edited by M. J. Schick, published by Marcel Dekker, Inc., New York, 1967 and McCutcheon's "Detergents and Emulsifiers", 1978, North American Edition, published by McCutcheon's Division, MC Publishing Corporation, Glen Rock, N.J., U.S.A.
Oil-soluble, water-insoluble functional additives are also well known. See, for example, the treatises by C. B. Smalheer and R. Kennedy Smith, published by Lezius-Hiles Co., Cleveland, Ohio, 1967, and by M. W. Ranney, published by Noyes Data Corp., Parkridge, N.J., 1973 entitled "Lubricant Additives". In this connection, and throughout the specification and appended claims, a water-insoluble functional additive is one which is not soluble in water above a level of about 1 gram per 100 milliliters of water at 25.degree. but is soluble in mineral oil to the extent of at least one gram per liter at 25.degree..